Effects of spontaneous otoacoustic emissions on distortion product otoacoustic emission

Objective: It has been reported that spontaneous otoacoustic emission (SOAE) can prolong the responses or increase the echo power of transiently evoked otoacoustic emission (TEOAE), yet the effects of SOAE on distortion product otoacoustic emission (DPOAE) have been studied less thoroughly. As most of the previous studies have not paid attention to the patient's age, sex and hearing level, they have not reflected possible effects of those factors. We studied the effects of SOAE specifically on DPOAE in the following subjects. Subjects and methods: The subjects were all females ranging in age from 19 to 24 (average: 21.4) and the 78 ears had a hearing threshold under 15 dB for 1, 2, and 4 kHz on pure-tone hearing test. IL088 (Otodynamics) was used for measurement of SOAE and IL092 (Otodynamics) for DPOAE. SOAEs were measured by time-averaging over 100 of the responses, of which those showing a clear peak 3 dB above the noise floor and being reproducible were considered as SOAE-positive. In all the ears, DPOAE responses were measured at L₁=L₂=70 dB, and in 42 ears also at L₁=L₂=60 dB and L₁/L₂=60/50 dB. The subjected ears were grouped into two by the presence or the absence of SOAE, and DPOAE amplitudes of 1, 2, and 4 kHz were compared, respectively. Results: Of the total, 39 ears were SOAE-positive and 39 SOAE-negative. Statistically no significant difference was observed in the average hearing level between the SOAE-positive and SOAE-negative groups. The hearing levels did not significantly differ in the frequencies of 1, 2, and 4 kHz, respectively, indicating that influence of the hearing level on DPOAE could be excludable. DPOAE amplitudes at L₁=L₂=70 dB in the frequencies of 1, 2, and 4 kHz were higher in the SOAE-positive group than in the SOAE-negative group. And DPOAE amplitudes were also higher in SOAE-positive group at L₁=L₂=60 dB and L₁/L₂=60/50 dB in the frequency of 1, 2, and 4 kHz, but significant differences were observed only in the frequencies of 4 kHz. By grouping the ears by the number of SOAE, we revealed the tendency that the larger the number of SOAE, the higher the DPOAE amplitudes. Conclusions: We evidenced that SOAE has significant effects on DPOAE responses. In clinical application of DPOAE measurement, therefore, the effects should be seriously taken into account.     

Isoflurane anesthesia suppresses distortion product otoacoustic emissions in rats

A commonly used anesthetic, isoflurane, can impair auditory function in a dose-dependent manner. However, in rats, isoflurane-induced auditory impairments have only been assessed with auditory brainstem responses; a measure which is unable to distinguish if changes originate from the central or peripheral auditory system. Studies performed in other species, such as mice and guinea-pigs, suggests auditory impairment stems from disrupted OHC amplification. Despite the wide use of the rat in auditory research, these observations have yet to be replicated in the rat animal model. This study used distortion product otoacoustic emissions to assess outer hair cell function in rats that were anesthetized with either isoflurane or a ketamine/xylazine cocktail for approximately 45?min. Results indicate that isoflurane can significantly reduce DPOAE amplitudes compared to ketamine/xylazine, and that responses were more variable with isoflurane than ketamine/xylazine over the 45-min test period. Based on these observations, isoflurane should be used with caution when assessing peripheral auditory function to avoid potentially confounding effects.     

Effects of cigarette smoking on distortion product otoacoustic emissions

This study measured distortion product otoacoustic emissions (DPOAEs) and DPOAE input/output (I/O) curves to assess the effects of smoking on cochlear function. Twenty-four healthy adults, 12 smokers and 12 nonsmokers in the 20-30 years age range were selected based on self-reported histories of five to eight years of smoking or no smoking, respectively. All subjects received tympanometric screening to rule out middle ear pathology. Conventional (0.25-8 kHz) and ultra high frequency (UHF; 10-20 kHz) audiometry showed normal or age-appropriate thresholds across both groups. DPOAE results showed small, but significant, decline in DPOAE levels without concomitant changes in noise floors in smokers as compared to nonsmokers. I/O detection thresholds were also significantly elevated at high frequencies in smokers as compared to their nonsmoking counterparts. These findings indicate that smokers are at greater risk for cochlear damage than nonsmokers, and that DPOAE amplitudes and I/O detection thresholds may identify early changes in cochlear function in smokers.     

选择注意对畸变产物耳声发射的影响

为研究高级中枢对耳蜗微机制的调控作用，对正常人１６例（３２耳）进行有和无视觉选择任务条件下的畸变学产物耳声发射（ＤＰＯＡＥ）测试，结果显示视觉任务了出现时ＤＰＯＡＥ幅值下降，Ｆ２为１，２ｋＨｚ处的ＤＰＯＡＥ幅值下降达显著性水平（Ｐ〈０．０５）。讨论了调控作用的可能机制，认为研究高级中枢和橄榄耳蜗传出神经系统对耳蜗功能的影响将有十分重要的生理和病理意义。     

Effects of noise on the intensity of distortion product otoacoustic emissions

Distortion product otoacoustic emission (DPOAE) is a widely used differential diagnostic method for diagnosing inner ear disorders. It provides us information on the condition of the outer hearing cells (OHCs). Otoacoustic emission occurs only when the OHCs are functioning normally. Changes in thresholds of DPOAE curves can provide us important information on the activity of the OHCs. The inner ear shows nonlinear properties if the OHCs are functioning normally. If OHCs are injured and thus function improperly, the system stops showing nonlinear properties. If we have a system with periodic excitation and, with the addition of white noise, the signal-to-noise ratio on the output increases (at least for small noise intensities), we have witnessed what is called phenomenon stochastic resonance. Our goal was to elucidate how white noise influences the intensity of DPOAE. If there is emission, that specific ear surely exhibits nonlinear behavior, which in turn is the basic property needed for stochastic resonance.     

Effects of chronic tobramycin treatment on distortion product otoacoustic emissions.

OBJECTIVE: To investigate the effects of chronic tobramycin treatment on distortion product otoacoustic emission (DPOAE) latencies and response growth detection thresholds in human subjects to determine the sensitivity of these DPOAE features to ototoxic damage. DESIGN: Six groups of children in two different age ranges were tested: three groups in the 7 to 14 yr age range, i.e., six children with normal hearing, four cystic fibrosis (CF) patients who received no aminoglycosides, and eight CF patients who received low- to moderate-cumulative doses of tobramycin (< 1250 mg/kg) for respiratory infections; and three groups of five subjects each in the 15 to 23 yr age range, i.e., the healthy group and the CF groups that received low- (< 285 mg/kg) and moderate-(1000 to 2000 mg/kg) cumulative drug dosages. The aggregate drug dosages compiled longitudinally over the past 5 yr were used to group the drug-treated CF patients. All subjects showed normal audiometric profiles (< or = 25 dB HL in the conventional frequency region and age-appropriate thresholds as described by Osterhammel and Osterhammel [1979] in the high-frequency region) and DP-grams (absolute DPOAE and noise amplitudes being consistent with the normative data obtained with the CUBeDIS system at this institution). RESULTS: Even though the audiometric profiles and DP-grams of all drug-treated CF groups were identical to their healthy counterparts, the DPOAE latencies and growth function thresholds showed significant changes. Whereas low and low-to-moderate doses of tobramycin were related to DPOAE latency prolongations, higher cumulative drug doses of 1000 to 2000 mg/kg produced significant reductions in DPOAE latencies. Response growth detection thresholds at high frequencies showed significant elevations in all CF patient groups treated with tobramycin, regardless of drug dosages, as compared with the control subjects. CONCLUSIONS: DPOAE amplitudes may not reflect the earliest changes produced by chronic aminoglycoside treatment, suggesting that cochlear ototoxicity may be more effectively monitored through the assessment of latencies and response growth detection thresholds. These findings pertain at least to the early stages of ototoxicity development, specifically during chronic tobramycin treatment. In light of the small sample size, however, these outcomes must be considered as tentative.     

Test-retest repeatability of distortion product otoacoustic emissions

OBJECTIVES: Distortion product otoacoustic emissions (DPOAE) have become part of routine audiological diagnostics. The large scale of clinical DPOAE applications, such as screening of hearing in infants, objective estimation of hearing status, distinction between cochlear and retrocochlear origin of sensorineural hearing loss, exclusion of psychogenic hearing loss, monitoring of hearing during administration of ototoxic drugs, and others illustrates the significance of this audiological tool. In all diagnostic tests, knowledge about the procedure's test-retest repeatability is of crucial importance, to allow for distinction between measurement deviations and true physiological or pathological changes in monitoring over time. DESIGN: Measurements of DPOAE were performed in triplicate in 80 normally hearing ears of 40 subjects. Both immediate remeasurements with the ear probe left in place [single-fit mode (SF-mode)] and remeasurements after approximately 5 to 10 days [multiple-fit mode (MF-mode)] were included. DPOAE primary tone levels were varied in 5 dB steps from L2 = 60 to 20 dB SPL (L1 = L2 x 0.4 + 39 dB SPL) and within the frequency range f2 = 1 to 6 kHz. Repeatability of DPOAE was evaluated by the standard error of measurement (Sm), reliability (Cronbach alpha), absolute differences between measurements, 95% confidence intervals, and repeatability standard deviations. RESULTS: Sm averaged 0.67 dB over all frequencies and primary tone levels in the SF-mode, and 1.44 dB in the MF-mode, respectively. As expected, test-retest repeatability declined with decreasing primary tone levels; however, repeatability values were still mostly satisfactory with the lower primary tone levels. For the exemplary primary tone level combination of L1/L2 = 63/60 dB SPL, which is close to common clinical paradigms, the difference between two DPOAE measurements under the reported test conditions could be considered statistically significant (p = 0.05) if it exceeded 0.7 to 1.3 dB in the range 1 to 5 kHz and 2.3 dB for 6 kHz in the SF-mode, when compared with 1.8 to 2.7 dB for 1 to 5 kHz and 3.7 dB for 6 kHz in the MF-mode. Signal to noise ratio (SNR) did not seem to have a large influence on repeatability, as long as SNR was within 6 to 35 dB, which covers the range of most clinical DPOAE measurements. CONCLUSIONS: The DPOAE-test-retest study presented here is to our knowledge the first, which combines variation of primary tone levels, assessment of both SF- and MF-modes, and comparison of the two modalities within the same subjects. Although the measurements were conducted under practical conditions resembling the clinical setting, repeatability was generally good. The widely used minimum SNR of 6 dB seems to be a recommendable criterion when considering both practicability and measurement quality under clinical conditions. The current findings underline the suitability of DPOAE as a monitoring tool of cochlear status over time. The data are intended to assist the clinician and the scientist in the correct interpretation of DPOAE level changes in the test-retest situation.     

Influence of spontaneous otoacoustic emissions on distortion product otoacoustic emission amplitudes

Although the influence of the levels and ratios of the primary stimulus on the amplitude of distortion product otoacoustic emissions (DPOAEs) has been studied intensely, the influence of the presence of spontaneous otoacoustic emissions (SOAEs) has been investigated less thoroughly. The present investigation analysed whether the unilateral presence of 58 SOAEs in 43 normal-hearing adults was related to larger DPOAEs in the ear with SOAEs compared to the contralateral ear having no SOAEs. The study was designed such that the only factor that could influence the amplitude of DPOAEs was the presence of SOAEs. Input/output (I/O) functions were collected in response to primary tones that were presented in 5-dB steps from 70 to 40 dB SPL at the frequency of the unilaterally recorded SOAE of each subject. The primary outcome was the demonstration of statistically significant (P<0.05) larger DPOAEs in ears exhibiting SOAEs than in ears without measurable SOAEs, except at the highest stimulus level of 70 dB SPL. These results suggest that SOAEs play an additive role in the measurement of DPOAEs. The enhancing effect of the unilateral presence of SOAEs on DPOAEs was statistically significant for 65 dB SPL and lower levels of primary tones. The authors speculate that passive cochlear properties begin to participate in the generation of DPOAEs at primary-stimulus levels greater than 65 dB SPL.     

畸变产物耳声发射与瞬态诱发耳声发射的相关性观察

目的：探讨畸变产物耳声发射（DPOAE)和瞬态诱发耳声发射(TEOAE)的特点和相关性。方法：以20例（40耳）耳科正常青年人观察噪声暴露前后在无对侧抑制（NCS)状态下和有对侧抑制（CS)状态下TEOAE的频带信噪比、频带反应幅值，与DPOAE的2f1-f2幅值、信噪比相互间的相关性。结果：DPOAE与TEOAE虽由不同的刺激声所引出，有各自的图形特征，但在绝大多数相近频率点上，其测量值有较好的相关性，形成一定的数量关系。结论：TEOAE测试较为快捷并有中频优势，而DPOAE则有很好的频率特异性和高频优势。二者幅值及信噪比间有良好的相关性，可得出有统计意义的线性回归方程参数，听觉损害，噪声性。     

Effects of sample size on the noise floor and distortion product otoacoustic emissions

This study investigated the effects of sample size on the noise floor and distortion product otoacoustic emissions (DPOAEs) in 55 normal-hearing subjects as a function of intensity. More specifically, we investigated the effects of sample size (12-400 sweeps) as a function of intensity (L1 = L2 = 35, 45 and 55 dB SPL), firstly, on the identifiability of DPOAEs (2F1-F2), secondly, on the noise floor adjacent to DPOAEs, and thirdly, on the magnitude of DPOAEs centred around geometric means of 531 Hz, 1,000 Hz, 2,000 Hz and 4,000 Hz. Testing was conducted with a commercially available system for measuring DPOAEs (Grason-Stadler, GSI-60). A constant F2:F1 ratio of 1.21 was used. As sample size increased from 12 to 400 sweeps, the noise floors decreased by about 13 dB; this closely corresponds to the expected 15 dB reduction based on the square root rule of noise reduction. The highest noise floors were measured at 531 Hz and the lowest noise floors at 2,000 Hz and 4,000 Hz. Identifiability increased as intensity increased from 35 to 55 dB SPL and as sample size increased from 12 to 400 sweeps for all stimulus conditions. Mean DPOAEs for all frequencies (531-4,000 Hz) appeared to decrease as sample size increased, particularly at stimulus levels of 35 dB and 45 dB SPL. These results may be explained by a reduction in the noise levels within the bandwidth of the DPOAE bin. That is, the DPOAE bin is comprised of the DPOAE plus background noise and these two quantities are not separated within the measured bin. Because the magnitude of bin containing DPOAEs is critically dependent on sample size, clinicians should carefully document this variable when collecting normative data. Similarly, clinicians who compare the magnitude of their DPOAEs to published data should note the sample size employed.     

畸变产物耳声发射的临床研究

畸变产物耳声发射（distortionProductotoacousticemissions，DPOAEs）为由两个纯音（F_1，F_2）同时刺激诱发的、由耳蜗外毛细胞能动活动产生的、在外耳道记录到的一种声能。与其它耳声发射相比其用于临床有以下优点：①潜伏期短；②可以连续评价任何频率，尤其是1～8kHz频率范围耳蜗功能；③可以完全评价刺激阈或刺激阈上水平的耳蜗功能（输入／输出功能曲线）；④听阈高达45～55dBHL，患者可以检测出，而瞬态诱发耳声发射（TEOAES）当听阈大于30dBHL时则测不出’‘’。所以DPOAES越来越多地受到人们的重视。巨DPOAES用于临…     

不同视觉任务及长时、重复测试对畸变产物耳声发射选择注意效应的影响

目的 :观察测试参数对畸变产物耳声发射 (DPOAEs)选择注意效应的影响。方法 :自行设计两种视觉任务 ,一种为计算机屏幕上的 O和 Q字母 ,另一种为红蓝灯装置。字母 Q和蓝灯为靶刺激 ,无规则出现 ,概率为2 0 % ;字母 O和红灯为非靶刺激 ,有规则出现 ,概率为 80 %。测试 7例正常人在有、无视觉任务出现时的DPOAEs。结果 :两种视觉任务均可使 DPOAEs幅值下降 ,两种设计间的差异无显著性意义 (P >0 .0 5 )。长时重复测试使选择注意效应减弱或消失。结论 :进行 DPOAEs选择注意效应测试时 ,应选择合适的视觉任务、较短的测试时间、较少的测试次数     

Effects of changes in stimulus level on phases of distortion product otoacoustic emissions

Effect of changes in stimulus levels of both lower (f(1)) and higher (f(2)) stimulus tones on phases of 2f(1)-f(2) component of the distortion product otoacoustic emission (DPOAE) was examined in five normal hearing adults. The f(2) was fixed at 4004 Hz in all of the measurements, and the stimulus frequency ratio (f(2)/f(1)) was varied from 1.15 to 1.3. Change of the level of lower stimulus tone (L(1)) and the level of higher stimulus tone (L(2)) showed different effects on the DPOAE phases. The phase lags increased with increasing L(1), when f(2)/f(1) was above 1.22, whereas the phase gains increased with increasing L(1), when f(2)/f(1) was below 1.22. On the other hand, the difference in L(2) minimally affected DPOAE phase at most f(1)s. The previous studies about basilar membrane vibration revealed that phase lags increase with increasing stimulus level, when the stimulus frequency is below the best frequency, while phase gains increase with increasing stimulus level, when the stimulus frequency is above the best frequency, and the effect of phase change in stimulus level diminished, when the stimulus frequency was far above the best frequency. Based on the comparison between the results of the present study and the previous findings of others concerning basilar membrane vibration, the DPOAE generation site is assumed to be located at apical of the peak of the f(2) traveling wave.     

The effect of impulse noise on distortion product otoacoustic emissions

The aim of this study was the evaluation of distortion product otoacoustic emissions (DPOAEs) before and after noise exposure from shooting, and the comparison of DPOAEs with pure-tone audiometry. Thirteen young male police officers were exposed to impulse noise from shooting, without using earplugs. Standard pure-tone audiometry, tympanometry, and DPOAEs were performed before exposure and at one hour post- and 24 hour post-exposure. In the one hour post-exposure testing mean pure-tone thresholds were elevated in the 1-8 kHz frequency zone and DPOAE levels were reduced at several frequencies. DPOAEs were more affected at 3 kHz or lower, whereas pure-tone thresholds were more affected at higher frequencies. After the final examination, non-significant partial shifts at high frequencies on both tests remained. Pure-tone audiometry was overall more sensitive, but DPOAEs provided additional information about the cochlear status of certain ears. These data suggest that besides behavioral testing, DPOAEs may play a role as a fast, objective, and easy to perform test for monitoring subjects exposed to impulse noise.     

The effect of impulse noise on distortion product otoacoustic emissions

The aim of this study was the evaluation of distortion product otoacoustic emissions (DPOAEs) before and after noise exposure from shooting, and the comparison of DPOAEs with pure-tone audiometry. Thirteen young male police officers were exposed to impulse noise from shooting, without using earplugs. Standard pure-tone audiometry, tympanometry, and DPOAEs were performed before exposure and at one hour post- and 24 hour post-exposure. In the one hour post-exposure testing mean pure-tone thresholds were elevated in the 1–8 kHz frequency zone and DPOAE levels were reduced at several frequencies. DPOAEs were more affected at 3 kHz or lower, whereas pure-tone thresholds were more affected at higher frequencies. After the final examination, non-significant partial shifts at high frequencies on both tests remained. Pure-tone audiometry was overall more sensitive, but DPOAEs provided additional information about the cochlear status of certain ears. These data suggest that besides behavioral testing, DPOAEs may play a role as a fast, objective, and easy to perform test for monitoring subjects exposed to impulse noise.     

The evaluation of distortion product otoacoustic emissions after stapedotomy

34 patients with otosclerosis operated at the ENT Clinic, were enrolled in this study. Prior and 4 months after stapedotomy the signal of DPOAE and the threshold levels for air and bone conduction were evaluated. No signal of otoacoustic emissions was registered in any of the patients prior stapedotomy. After operation DPOAE was registered in 23 out of 34 examined patients (67.6%).     

Sensitivity of distortion product otoacoustic emissions in noise-exposed chinchillas

The present study investigates the effect of small amounts of outer hair cell (OHC) loss on distortion product otoacoustic emission (DPOAE) levels and evoked potential permanent threshold shifts (PTS) in a population of 12 noise-exposed chinchillas. The group mean DPOAE level, which decreased by up to approximately 15 dB in the presence of less than 8 dB PTS and 15% OHC loss, indicates that DPOAEs can detect an underlying cochlear pathology (i,e., OHC damage/loss) despite the presence of normal to near normal thresholds. The sensitivity of DPOAEs in detecting OHC loss makes this test measure suited for diagnosing sensorineural hearing impairment, particularly when abnormal auditory symptoms (i.e., speech discrimination problems) are associated with a normal audiogram in the clinical setting and as part of a hearing conservation program.     

早产儿畸变产物耳声发射的特性分析

目的 :研究早产儿畸变产物耳声发射 (DPOAE)的幅值、信噪比、本底噪声等基本特性。方法 :应用DP2 0 0 0型耳声发射仪对 31例早产儿 (5 9耳 )和 19例足月新生儿 (35耳 )在出生后 3d～ 1周内行DPOAE检测。结果 :早产儿DPOAE反应幅值曲线有一峰点 (f2 =15 87Hz)和一谷点 (f2 =4 0 0 0Hz) ,早产儿各频率反应幅值均低于足月新生儿相应频率 (P <0 .0 5 ) ;早产儿DPOAE信噪比SNR于f2 =4 0 0 0Hz处最高 ,f2 =10 0 0Hz处最低 ,4 0 0 0Hz、3175Hz及 15 87Hz、12 6 0Hz、10 0 0Hz处SNR均低于足月儿相应水平 (P <0 .0 5 ) ;早产儿DPOAE本底噪声在低频段 (f2 =12 6 0Hz、10 0 0Hz)显著高于其他频率 ,4 0 0 0Hz处噪声水平最低 (P <0 .0 1) ,3175Hz、2 5 2 0Hz及 2 0 0 0Hz处早产儿组噪声水平均低于足月儿组 (P <0 .0 5 )。结论 :早产儿DPOAE反应幅值、信噪比及本底噪声与足月儿相比差异均有统计学意义。该差异与耳蜗外毛细胞发育过程相关 ,还可能与中耳及外耳的发育有关     

豚鼠畸变产物耳声发射的检测

目的 :建立稳定可靠的检测动物畸变产物耳声发射的方法。方法 :采用预先手术切除耳屏软骨 ,加用自制探头套管 ,选择复合麻醉等改良方法 ,测量健康杂色豚鼠 7只 ( 13耳 ) 2、4、6k Hz畸变产物耳声发射( DPOAE)输入输出 ( I/ O )曲线、潜伏期等指标。结果 :各频率 DPOAE引出率均为 10 0 % ,I/ O曲线最大幅值分别为 ( 2 7.2 4± 4 .15 ) d B SPL ,( 2 7.98± 4 .0 5 ) d B SPL和 ( 4 1.4 5± 1.2 0 ) d B SPL ;潜伏期为 ( 2 .0 6± 0 .2 1) m s,( 1.5 2±0 .16) ms和 ( 1.3 7± 0 .0 8) m s。结论 :改良法豚鼠 DPOAE检出率高 ,振幅大 ,各指标结果重复性好 ,适用于动物DPOAE的研究。     

不同视觉任务及长时,重复测试对畸变产物耳声发射选择注？…

目的：观察测试参数对畸变产物声发射（ＤＰＯＡＥＳ）选择注意效应的影响。方法：自行设计两种视觉任务,一种为计算机屏幕上的Ｏ和Ｑ字母,另一种为红蓝灯装置。字母Ｑ和蓝灯为靶刺激,无规则出现,概率为２０％;字母Ｏ和红灯为非靶刺激,有规则出现,概率为８０％。测试７例正常人在有、无视觉任务出现时的ＤＰＯＡＥＳ。结果：两种视觉任务均可使ＤＰＯＡＥＳ幅值下降,两种设计间的差异无显著性意义。长时重复测试使选择注意效